1. Field of the Disclosure
The present disclosure relates to a method of manufacturing components for gas turbine engines and, in particular, to a method of manufacturing a leading edge for an aerofoil component.
2. Description of the Related Art
With reference to FIG. 1, a ducted fan gas turbine engine is generally indicated at 10 and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustion equipment 15, a high-pressure turbine 16, an intermediate pressure turbine 17, a low-pressure turbine 18 and a core engine exhaust nozzle 19. A nacelle 21 generally surrounds the engine 10 and defines the intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.
During operation, air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate pressure compressor 13 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.
The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16, 17, 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.
Aerofoil components include blades and vanes which are incorporated in the propulsive fan 12, compressors 13, 14 and turbines 16, 17, 18.
As shown in FIG. 2 (which is cross-section through the leading edge of an aerofoil component), these aerofoil components each comprise a suction surface 25 and an opposing pressure surface 26 which meet at a leading edge 37 and a trailing edge (not shown), the two edges being axially opposed to one another. The aerofoil components are typically formed from cast or forged stock (which has the profile 38 shown in dotted lines in FIG. 2) which is processed to form a pre-form having a sharp precursor edge 39. This precursor edge 39 is subsequently processed to produce a radius e.g. to form a leading edge 37 with an elliptical profile.
Using this known method makes it difficult to reliably and consistently obtain the optimum profile of the leading edge. The processing of the cast or forged stock to create the pre-form takes no account of the quality or conformance of the cast/forged stock and thus the precursor edge can vary from the desired profile. Similarly, subsequent processing of the pre-form to create the leading edge takes no account of any variance of the precursor edge from the desired profile and thus it is difficult to ensure that the leading edge is formed with the optimum profile. Any deviation from the optimum profile of the leading edge can result in sub-optimal aerodynamic performance of the component which, in turn, leads to sub-optimal efficiency of the gas turbine engine.
In addition, the known method is difficult to apply at the portions of an aerofoil component where the leading edge joins the filleted mounting portions of the component (which are provided to mount at least one end of the component within the fan/compressor/turbine).
Metal Injection Moulding (MIM) is a known technique for producing metal components. Metal powder is mixed with a thermoplastic binder to generate a feedstock which is subsequently shaped by injection into a die to create a ‘green’ component. The green component is treated (e.g. thermally or chemically) to remove the binder and is then subjected to a sintering treatment to consolidate the metal and form the metal component (which may be subsequently surface finished).